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Date:   Sun, 17 Mar 2019 00:14:37 +0200
From:   Sakari Ailus <sakari.ailus@iki.fi>
To:     Mickael Guene <mickael.guene@st.com>
Cc:     linux-media@vger.kernel.org,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Matt Ranostay <matt.ranostay@konsulko.com>,
        linux-kernel@vger.kernel.org, Ben Kao <ben.kao@intel.com>,
        Todor Tomov <todor.tomov@linaro.org>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Rui Miguel Silva <rui.silva@linaro.org>,
        Akinobu Mita <akinobu.mita@gmail.com>,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        Jason Chen <jasonx.z.chen@intel.com>,
        Jacopo Mondi <jacopo+renesas@jmondi.org>,
        Tianshu Qiu <tian.shu.qiu@intel.com>,
        Bingbu Cao <bingbu.cao@intel.com>
Subject: Re: [PATCH v1 2/3] media:st-mipid02: MIPID02 CSI-2 to PARALLEL
 bridge driver
Message-ID: <20190316221437.e3ukdpgyn2yq72tu@valkosipuli.retiisi.org.uk>
References: <1552373045-134493-1-git-send-email-mickael.guene@st.com>
 <1552373045-134493-3-git-send-email-mickael.guene@st.com>
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In-Reply-To: <1552373045-134493-3-git-send-email-mickael.guene@st.com>
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Hi Mickael,

Thanks for the patchset.

On Tue, Mar 12, 2019 at 07:44:04AM +0100, Mickael Guene wrote:
> This V4L2 subdev driver enables STMicroelectronics MIPID02 device.
> 
> Signed-off-by: Mickael Guene <mickael.guene@st.com>
> ---
> 
>  drivers/media/i2c/Kconfig      |  13 +
>  drivers/media/i2c/Makefile     |   1 +
>  drivers/media/i2c/st-mipid02.c | 878 +++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 892 insertions(+)
>  create mode 100644 drivers/media/i2c/st-mipid02.c
> 
> diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig
> index 6d32f8d..11a2376 100644
> --- a/drivers/media/i2c/Kconfig
> +++ b/drivers/media/i2c/Kconfig
> @@ -1132,6 +1132,19 @@ config VIDEO_I2C
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called video-i2c
>  
> +config VIDEO_ST_MIPID02
> +	tristate "STMicroelectronics MIPID02 CSI-2 to PARALLEL bridge"
> +	depends on I2C && VIDEO_V4L2 && VIDEO_V4L2_SUBDEV_API
> +	depends on MEDIA_CAMERA_SUPPORT
> +	depends on MEDIA_CONTROLLER
> +	select V4L2_FWNODE
> +	help
> +	  Support for STMicroelectronics MIPID02 CSI-2 to PARALLEL bridge.
> +	  It is used to allow usage of CSI-2 sensor with PARALLEL port controller.

Over 80, please wrap.

> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called st-mipid02.
> +
>  endmenu
>  
>  endif
> diff --git a/drivers/media/i2c/Makefile b/drivers/media/i2c/Makefile
> index a64fca8..d8ad9da 100644
> --- a/drivers/media/i2c/Makefile
> +++ b/drivers/media/i2c/Makefile
> @@ -113,5 +113,6 @@ obj-$(CONFIG_VIDEO_IMX258)	+= imx258.o
>  obj-$(CONFIG_VIDEO_IMX274)	+= imx274.o
>  obj-$(CONFIG_VIDEO_IMX319)	+= imx319.o
>  obj-$(CONFIG_VIDEO_IMX355)	+= imx355.o
> +obj-$(CONFIG_VIDEO_ST_MIPID02) += st-mipid02.o
>  
>  obj-$(CONFIG_SDR_MAX2175) += max2175.o
> diff --git a/drivers/media/i2c/st-mipid02.c b/drivers/media/i2c/st-mipid02.c
> new file mode 100644
> index 0000000..d8710fe
> --- /dev/null
> +++ b/drivers/media/i2c/st-mipid02.c
> @@ -0,0 +1,878 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Driver for ST MIPID02 CSI-2 to PARALLEL bridge
> + *
> + * Copyright (C) STMicroelectronics SA 2019
> + * Authors: Mickael Guene <mickael.guene@st.com>
> + *          for STMicroelectronics.
> + *
> + *
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/of_graph.h>
> +#include <linux/regulator/consumer.h>
> +#include <media/v4l2-async.h>
> +#include <media/v4l2-ctrls.h>
> +#include <media/v4l2-device.h>
> +#include <media/v4l2-fwnode.h>
> +#include <media/v4l2-subdev.h>
> +
> +#define MIPID02_CLK_LANE_WR_REG1			0x01
> +#define MIPID02_CLK_LANE_REG1				0x02
> +#define MIPID02_CLK_LANE_REG3				0x04
> +#define MIPID02_DATA_LANE0_REG1				0x05
> +#define MIPID02_DATA_LANE0_REG2				0x06
> +#define MIPID02_DATA_LANE1_REG1				0x09
> +#define MIPID02_DATA_LANE1_REG2				0x0a
> +#define MIPID02_MODE_REG1				0x14
> +#define MIPID02_MODE_REG2				0x15
> +#define MIPID02_DATA_ID_RREG				0x17
> +#define MIPID02_DATA_SELECTION_CTRL			0x19
> +#define MIPID02_PIX_WIDTH_CTRL				0x1e
> +#define MIPID02_PIX_WIDTH_CTRL_EMB			0x1f
> +
> +/* Bits definition for MIPID02_CLK_LANE_REG1 */
> +#define CLK_ENABLE					BIT(0)
> +/* Bits definition for MIPID02_CLK_LANE_REG3 */
> +#define CLK_MIPI_CSI					BIT(1)
> +/* Bits definition for MIPID02_DATA_LANE0_REG1 */
> +#define DATA_ENABLE					BIT(0)
> +/* Bits definition for MIPID02_DATA_LANEx_REG2 */
> +#define DATA_MIPI_CSI					BIT(0)
> +/* Bits definition for MIPID02_MODE_REG1 */
> +#define MODE_DATA_SWAP					BIT(2)
> +#define MODE_NO_BYPASS					BIT(6)
> +/* Bits definition for MIPID02_MODE_REG2 */
> +#define MODE_HSYNC_ACTIVE_HIGH				BIT(1)
> +#define MODE_VSYNC_ACTIVE_HIGH				BIT(2)
> +/* Bits definition for MIPID02_DATA_SELECTION_CTRL */
> +#define SELECTION_MANUAL_DATA				BIT(2)
> +#define SELECTION_MANUAL_WIDTH				BIT(3)
> +
> +/* regulator supplies */
> +static const char * const mipid02_supply_name[] = {
> +	"VDDE", /* 1.8V digital I/O supply */
> +	"VDDIN", /* 1V8 voltage regulator supply */
> +};
> +
> +#define MIPID02_NUM_SUPPLIES		ARRAY_SIZE(mipid02_supply_name)
> +#define MIPID02_PAD_NB			2
> +
> +struct mipid02_dev {
> +	struct i2c_client *i2c_client;
> +	struct regulator_bulk_data supplies[MIPID02_NUM_SUPPLIES];
> +	struct v4l2_subdev sd;
> +	struct media_pad pad[MIPID02_PAD_NB];
> +	struct clk *xclk;
> +	struct gpio_desc *reset_gpio;
> +	/* Protect streaming */
> +	struct mutex lock;
> +	bool streaming;
> +	/* endpoints info */
> +	struct v4l2_fwnode_endpoint rx;
> +	u64 link_frequency;
> +	struct v4l2_fwnode_endpoint tx;
> +	/* remote source */
> +	struct v4l2_async_subdev asd;
> +	struct v4l2_async_notifier notifier;
> +	/* registers */
> +	struct {
> +		u8 clk_lane_reg1;
> +		u8 data_lane0_reg1;
> +		u8 data_lane1_reg1;
> +		u8 mode_reg1;
> +		u8 mode_reg2;
> +		u8 data_id_rreg;
> +		u8 pix_width_ctrl;
> +		u8 pix_width_ctrl_emb;
> +	} r;
> +};
> +
> +static int bpp_from_code(__u32 code)
> +{
> +	switch (code) {
> +	case MEDIA_BUS_FMT_SBGGR8_1X8:
> +	case MEDIA_BUS_FMT_SGBRG8_1X8:
> +	case MEDIA_BUS_FMT_SGRBG8_1X8:
> +	case MEDIA_BUS_FMT_SRGGB8_1X8:
> +		return 8;
> +	case MEDIA_BUS_FMT_SBGGR10_1X10:
> +	case MEDIA_BUS_FMT_SGBRG10_1X10:
> +	case MEDIA_BUS_FMT_SGRBG10_1X10:
> +	case MEDIA_BUS_FMT_SRGGB10_1X10:
> +		return 10;
> +	case MEDIA_BUS_FMT_SBGGR12_1X12:
> +	case MEDIA_BUS_FMT_SGBRG12_1X12:
> +	case MEDIA_BUS_FMT_SGRBG12_1X12:
> +	case MEDIA_BUS_FMT_SRGGB12_1X12:
> +		return 12;
> +	case MEDIA_BUS_FMT_UYVY8_2X8:
> +		return 16;
> +	case MEDIA_BUS_FMT_BGR888_1X24:
> +		return 24;
> +	default:
> +		return 0;
> +	}
> +}
> +
> +static u8 data_type_from_code(__u32 code)
> +{
> +	switch (code) {
> +	case MEDIA_BUS_FMT_SBGGR8_1X8:
> +	case MEDIA_BUS_FMT_SGBRG8_1X8:
> +	case MEDIA_BUS_FMT_SGRBG8_1X8:
> +	case MEDIA_BUS_FMT_SRGGB8_1X8:
> +		return 0x2a;
> +	case MEDIA_BUS_FMT_SBGGR10_1X10:
> +	case MEDIA_BUS_FMT_SGBRG10_1X10:
> +	case MEDIA_BUS_FMT_SGRBG10_1X10:
> +	case MEDIA_BUS_FMT_SRGGB10_1X10:
> +		return 0x2b;
> +	case MEDIA_BUS_FMT_SBGGR12_1X12:
> +	case MEDIA_BUS_FMT_SGBRG12_1X12:
> +	case MEDIA_BUS_FMT_SGRBG12_1X12:
> +	case MEDIA_BUS_FMT_SRGGB12_1X12:
> +		return 0x2c;
> +	case MEDIA_BUS_FMT_UYVY8_2X8:
> +		return 0x1e;
> +	case MEDIA_BUS_FMT_BGR888_1X24:
> +		return 0x24;
> +	default:
> +		return 0;
> +	}
> +}
> +
> +static inline struct mipid02_dev *to_mipid02_dev(struct v4l2_subdev *sd)
> +{
> +	return container_of(sd, struct mipid02_dev, sd);
> +}
> +
> +static int mipid02_read_reg(struct mipid02_dev *bridge, u16 reg, u8 *val)
> +{
> +	struct i2c_client *client = bridge->i2c_client;
> +	struct i2c_msg msg[2];
> +	u8 buf[2];
> +	int ret;
> +
> +	buf[0] = reg >> 8;
> +	buf[1] = reg & 0xff;
> +
> +	msg[0].addr = client->addr;
> +	msg[0].flags = client->flags;
> +	msg[0].buf = buf;
> +	msg[0].len = sizeof(buf);
> +
> +	msg[1].addr = client->addr;
> +	msg[1].flags = client->flags | I2C_M_RD;
> +	msg[1].buf = val;
> +	msg[1].len = 1;
> +
> +	ret = i2c_transfer(client->adapter, msg, 2);
> +	if (ret < 0) {
> +		dev_dbg(&client->dev, "%s: %x i2c_transfer, reg: %x => %d\n",
> +			    __func__, client->addr, reg, ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int mipid02_write_reg(struct mipid02_dev *bridge, u16 reg, u8 val)
> +{
> +	struct i2c_client *client = bridge->i2c_client;
> +	struct i2c_msg msg;
> +	u8 buf[3];
> +	int ret;
> +
> +	buf[0] = reg >> 8;
> +	buf[1] = reg & 0xff;
> +	buf[2] = val;
> +
> +	msg.addr = client->addr;
> +	msg.flags = client->flags;
> +	msg.buf = buf;
> +	msg.len = sizeof(buf);
> +
> +	ret = i2c_transfer(client->adapter, &msg, 1);
> +	if (ret < 0) {
> +		dev_dbg(&client->dev, "%s: i2c_transfer, reg: %x => %d\n",
> +			    __func__, reg, ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int mipid02_get_regulators(struct mipid02_dev *bridge)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < MIPID02_NUM_SUPPLIES; i++)
> +		bridge->supplies[i].supply = mipid02_supply_name[i];
> +
> +	return devm_regulator_bulk_get(&bridge->i2c_client->dev,
> +				       MIPID02_NUM_SUPPLIES,
> +				       bridge->supplies);
> +}
> +
> +static void mipid02_apply_reset(struct mipid02_dev *bridge)
> +{
> +	gpiod_set_value_cansleep(bridge->reset_gpio, 0);
> +	usleep_range(5000, 10000);
> +	gpiod_set_value_cansleep(bridge->reset_gpio, 1);
> +	usleep_range(5000, 10000);
> +	gpiod_set_value_cansleep(bridge->reset_gpio, 0);
> +}
> +
> +static int mipid02_set_power_on(struct mipid02_dev *bridge)
> +{
> +	struct i2c_client *client = bridge->i2c_client;
> +	int ret;
> +
> +	ret = clk_prepare_enable(bridge->xclk);
> +	if (ret) {
> +		dev_err(&client->dev, "%s: failed to enable clock\n", __func__);
> +		return ret;
> +	}
> +
> +	ret = regulator_bulk_enable(MIPID02_NUM_SUPPLIES,
> +				    bridge->supplies);
> +	if (ret) {
> +		dev_err(&client->dev, "%s: failed to enable regulators\n",
> +			    __func__);
> +		goto xclk_off;
> +	}
> +
> +	if (bridge->reset_gpio) {
> +		dev_dbg(&client->dev, "apply reset");
> +		mipid02_apply_reset(bridge);
> +	} else {
> +		dev_dbg(&client->dev, "dont apply reset");
> +		usleep_range(5000, 10000);
> +	}
> +
> +	return 0;
> +
> +xclk_off:
> +	clk_disable_unprepare(bridge->xclk);
> +	return ret;
> +}
> +
> +static void mipid02_set_power_off(struct mipid02_dev *bridge)
> +{
> +	regulator_bulk_disable(MIPID02_NUM_SUPPLIES, bridge->supplies);
> +	clk_disable_unprepare(bridge->xclk);
> +}
> +
> +static int mipid02_detect(struct mipid02_dev *bridge)
> +{
> +	u8 reg;
> +
> +	/*
> +	 * There is no version registers. Just try to read register
> +	 * MIPID02_CLK_LANE_WR_REG1.
> +	 */
> +	return mipid02_read_reg(bridge, MIPID02_CLK_LANE_WR_REG1, &reg);
> +}
> +
> +static u32 mipid02_get_link_freq_from_rx_ep(struct mipid02_dev *bridge)
> +{
> +	struct v4l2_fwnode_endpoint *ep = &bridge->rx;
> +
> +	if (ep->nr_of_link_frequencies != 1)
> +		return 0;
> +
> +	return ep->link_frequencies[0];
> +}
> +
> +static u32 mipid02_get_link_freq_from_cid_link_freq(struct mipid02_dev *bridge,
> +						    struct v4l2_subdev *sensor)
> +{
> +	struct v4l2_ctrl *ctrl;
> +
> +	ctrl = v4l2_ctrl_find(sensor->ctrl_handler, V4L2_CID_LINK_FREQ);
> +	if (!ctrl)
> +		return 0;
> +
> +	return v4l2_ctrl_g_ctrl_int64(ctrl);
> +}
> +
> +static u32 mipid02_get_link_freq_from_cid_pixel_rate(struct mipid02_dev *bridge,
> +						     __u32 code,
> +						     struct v4l2_subdev *sensor)
> +{
> +	struct v4l2_fwnode_endpoint *ep = &bridge->rx;
> +	struct v4l2_ctrl *ctrl;
> +	u32 pixel_clock;
> +	u32 bpp = bpp_from_code(code);
> +
> +	ctrl = v4l2_ctrl_find(sensor->ctrl_handler, V4L2_CID_PIXEL_RATE);
> +	if (!ctrl)
> +		return 0;
> +	pixel_clock = v4l2_ctrl_g_ctrl_int64(ctrl);
> +
> +	return pixel_clock * bpp / (2 * ep->bus.mipi_csi2.num_data_lanes);
> +}
> +
> +/*
> + * We need to know link frequency to setup clk_lane_reg1 timings. So use
> + * following sequence, stop when we got a frequency.
> + *  - Get it from device tree. It allow to connect sensor without support of
> + *    V4L2_CID_LINK_FREQ or V4L2_CID_PIXEL_RATE or with a broken one. Drawback
> + *    is that is that link frequency must be constant.
> + *  - Get it from V4L2_CID_LINK_FREQ.
> + *  - Get it from V4L2_CID_PIXEL_RATE and use bit per pixel and number of lanes
> + *    to compute it.
> + */
> +static int mipid02_configure_from_rx_speed(struct mipid02_dev *bridge,
> +					   __u32 code,
> +					   struct v4l2_subdev *sensor)
> +{
> +	struct i2c_client *client = bridge->i2c_client;
> +	u32 link_freq;
> +
> +	link_freq = mipid02_get_link_freq_from_rx_ep(bridge);
> +	if (link_freq)
> +		goto success;
> +
> +	link_freq = mipid02_get_link_freq_from_cid_link_freq(bridge, sensor);
> +	if (link_freq)
> +		goto success;
> +
> +	link_freq = mipid02_get_link_freq_from_cid_pixel_rate(bridge, code,
> +							      sensor);
> +	if (link_freq)
> +		goto success;
> +	dev_err(&client->dev, "Failed to detect link frequency");
> +
> +	return -EINVAL;
> +
> +success:
> +	dev_dbg(&client->dev, "detect link_freq = %d Hz", link_freq);
> +	bridge->r.clk_lane_reg1 |= (2000000000 / link_freq) << 2;
> +
> +	return 0;
> +}
> +
> +static int mipid02_configure_clk_lane(struct mipid02_dev *bridge)
> +{
> +	struct i2c_client *client = bridge->i2c_client;
> +	struct v4l2_fwnode_endpoint *ep = &bridge->rx;
> +	bool *polarities = ep->bus.mipi_csi2.lane_polarities;
> +
> +	/* midid02 doesn't support clock lane remapping */
> +	if (ep->bus.mipi_csi2.clock_lane != 0) {
> +		dev_err(&client->dev, "clk lane must be map to lane 0\n");
> +		return -EINVAL;
> +	}
> +	bridge->r.clk_lane_reg1 |= (polarities[0] << 1) | CLK_ENABLE;
> +
> +	return 0;
> +}
> +
> +static int mipid02_configure_data0_lane(struct mipid02_dev *bridge, int nb,
> +					bool are_lanes_swap, bool *polarities)
> +{
> +	bool are_pin_swap = are_lanes_swap ? polarities[2] : polarities[1];
> +
> +	if (nb == 1 && are_lanes_swap)
> +		return 0;
> +
> +	/*
> +	 * data lane 0 as pin swap polarity reversed compared to clock and
> +	 *data lane 1
> +	 */
> +	if (!are_pin_swap)
> +		bridge->r.data_lane0_reg1 = 1 << 1;
> +	bridge->r.data_lane0_reg1 |= DATA_ENABLE;
> +
> +	return 0;
> +}
> +
> +static int mipid02_configure_data1_lane(struct mipid02_dev *bridge, int nb,
> +					bool are_lanes_swap, bool *polarities)
> +{
> +	bool are_pin_swap = are_lanes_swap ? polarities[1] : polarities[2];
> +
> +	if (nb == 1 && !are_lanes_swap)
> +		return 0;
> +
> +	if (are_pin_swap)
> +		bridge->r.data_lane1_reg1 = 1 << 1;
> +	bridge->r.data_lane1_reg1 |= DATA_ENABLE;
> +
> +	return 0;
> +}
> +
> +static int mipid02_configure_from_rx(struct mipid02_dev *bridge, __u32 code,
> +				     struct v4l2_subdev *sensor)
> +{
> +	struct v4l2_fwnode_endpoint *ep = &bridge->rx;
> +	bool are_lanes_swap = ep->bus.mipi_csi2.data_lanes[0] == 2;
> +	bool *polarities = ep->bus.mipi_csi2.lane_polarities;
> +	int nb = ep->bus.mipi_csi2.num_data_lanes;
> +	int ret;
> +
> +	ret = mipid02_configure_clk_lane(bridge);
> +	if (ret)
> +		return ret;
> +
> +	ret = mipid02_configure_data0_lane(bridge, nb, are_lanes_swap,
> +					   polarities);
> +	if (ret)
> +		return ret;
> +
> +	ret = mipid02_configure_data1_lane(bridge, nb, are_lanes_swap,
> +					   polarities);
> +	if (ret)
> +		return ret;
> +
> +	bridge->r.mode_reg1 |= are_lanes_swap ? MODE_DATA_SWAP : 0;
> +	bridge->r.mode_reg1 |= (nb - 1) << 1;
> +
> +	return mipid02_configure_from_rx_speed(bridge, code, sensor);
> +}
> +
> +static int mipid02_configure_from_tx(struct mipid02_dev *bridge)
> +{
> +	struct v4l2_fwnode_endpoint *ep = &bridge->tx;
> +
> +	bridge->r.pix_width_ctrl = ep->bus.parallel.bus_width;
> +	bridge->r.pix_width_ctrl_emb = ep->bus.parallel.bus_width;
> +	if (ep->bus.parallel.flags & V4L2_MBUS_HSYNC_ACTIVE_HIGH)
> +		bridge->r.mode_reg2 |= MODE_HSYNC_ACTIVE_HIGH;
> +	if (ep->bus.parallel.flags & V4L2_MBUS_VSYNC_ACTIVE_HIGH)
> +		bridge->r.mode_reg2 |= MODE_VSYNC_ACTIVE_HIGH;
> +
> +	return 0;
> +}
> +
> +static int mipid02_configure_from_code(struct mipid02_dev *bridge, __u32 code)
> +{
> +	u8 data_type;
> +
> +	bridge->r.data_id_rreg = 0;
> +	data_type = data_type_from_code(code);
> +	if (!data_type)
> +		return -EINVAL;
> +	bridge->r.data_id_rreg = data_type;
> +
> +	return 0;
> +}
> +
> +static __u32 mipid02_get_source_code(struct mipid02_dev *bridge,
> +				     struct v4l2_subdev *sensor)
> +{
> +	int ret;

Please declare temporary variables, return values etc. as last. That
generally is the case elsewhere in the file.

> +	struct v4l2_subdev_format fmt = {
> +		.which = V4L2_SUBDEV_FORMAT_ACTIVE,
> +	};
> +
> +	ret = v4l2_subdev_call(sensor, pad, get_fmt, NULL, &fmt);
> +
> +	return ret ? MEDIA_BUS_FMT_SBGGR8_1X8 : fmt.format.code;
> +}
> +
> +static int mipid02_stream_disable(struct mipid02_dev *bridge)
> +{
> +	struct i2c_client *client = bridge->i2c_client;
> +	int ret = 0;

No need to initialise here.

> +
> +	/* Disable all lanes */
> +	ret |= mipid02_write_reg(bridge, MIPID02_CLK_LANE_REG1, 0);
> +	ret |= mipid02_write_reg(bridge, MIPID02_DATA_LANE0_REG1, 0);
> +	ret |= mipid02_write_reg(bridge, MIPID02_DATA_LANE1_REG1, 0);
> +	if (ret)
> +		dev_err(&client->dev, "failed to stream off %d", ret);
> +
> +	return ret;
> +}
> +
> +static struct v4l2_subdev *mipid02_find_sensor(struct mipid02_dev *bridge)
> +{
> +	struct media_device *mdev = bridge->sd.v4l2_dev->mdev;
> +	struct media_entity *entity;
> +
> +	if (!mdev)
> +		return NULL;
> +
> +	media_device_for_each_entity(entity, mdev)
> +		if (entity->function == MEDIA_ENT_F_CAM_SENSOR)
> +			return media_entity_to_v4l2_subdev(entity);

Hmm. Could you instead use the link state to determine which of the
receivers is active? You'll need one more pad, and then you'd had 1:1
mapping between ports and pads.

> +
> +	return NULL;
> +}
> +
> +static int mipid02_stream_enable(struct mipid02_dev *bridge)
> +{
> +	struct i2c_client *client = bridge->i2c_client;
> +	struct v4l2_subdev *sensor;
> +	__u32 code;
> +	int ret = 0;

No need to initialise.

> +
> +	sensor = mipid02_find_sensor(bridge);
> +	if (!sensor)
> +		goto error;
> +
> +	dev_dbg(&client->dev, "use sensor '%s'", sensor->name);
> +	memset(&bridge->r, 0, sizeof(bridge->r));
> +	/* build registers content */
> +	code = mipid02_get_source_code(bridge, sensor);
> +	ret |= mipid02_configure_from_rx(bridge, code, sensor);
> +	ret |= mipid02_configure_from_tx(bridge);
> +	ret |= mipid02_configure_from_code(bridge, code);
> +
> +	/* write mipi registers */
> +	ret |= mipid02_write_reg(bridge, MIPID02_CLK_LANE_REG1,
> +		bridge->r.clk_lane_reg1);
> +	ret |= mipid02_write_reg(bridge, MIPID02_CLK_LANE_REG3, CLK_MIPI_CSI);
> +	ret |= mipid02_write_reg(bridge, MIPID02_DATA_LANE0_REG1,
> +		bridge->r.data_lane0_reg1);
> +	ret |= mipid02_write_reg(bridge, MIPID02_DATA_LANE0_REG2,
> +		DATA_MIPI_CSI);
> +	ret |= mipid02_write_reg(bridge, MIPID02_DATA_LANE1_REG1,
> +		bridge->r.data_lane1_reg1);
> +	ret |= mipid02_write_reg(bridge, MIPID02_DATA_LANE1_REG2,
> +		DATA_MIPI_CSI);
> +	ret |= mipid02_write_reg(bridge, MIPID02_MODE_REG1,
> +		MODE_NO_BYPASS | bridge->r.mode_reg1);
> +	ret |= mipid02_write_reg(bridge, MIPID02_MODE_REG2,
> +		bridge->r.mode_reg2);
> +	ret |= mipid02_write_reg(bridge, MIPID02_DATA_ID_RREG,
> +		bridge->r.data_id_rreg);
> +	ret |= mipid02_write_reg(bridge, MIPID02_DATA_SELECTION_CTRL,
> +		SELECTION_MANUAL_DATA | SELECTION_MANUAL_WIDTH);
> +	ret |= mipid02_write_reg(bridge, MIPID02_PIX_WIDTH_CTRL,
> +		bridge->r.pix_width_ctrl);
> +	ret |= mipid02_write_reg(bridge, MIPID02_PIX_WIDTH_CTRL_EMB,
> +		bridge->r.pix_width_ctrl_emb);

Be careful with the error codes. ret will be returned by the s_stream
callback below.

> +
> +	if (ret)
> +		goto error;
> +
> +	return 0;
> +
> +error:
> +	dev_err(&client->dev, "failed to stream on %d", ret);
> +	mipid02_stream_disable(bridge);
> +
> +	return ret;
> +}
> +
> +static int mipid02_s_stream(struct v4l2_subdev *sd, int enable)
> +{
> +	struct mipid02_dev *bridge = to_mipid02_dev(sd);
> +	struct i2c_client *client = bridge->i2c_client;
> +	int ret = 0;
> +
> +	dev_dbg(&client->dev, "%s : requested %d / current = %d", __func__,
> +		    enable, bridge->streaming);
> +	mutex_lock(&bridge->lock);
> +
> +	if (bridge->streaming == enable)
> +		goto out;
> +
> +	ret = enable ? mipid02_stream_enable(bridge) :
> +		       mipid02_stream_disable(bridge);
> +	if (!ret)
> +		bridge->streaming = enable;
> +
> +out:
> +	dev_dbg(&client->dev, "%s current now = %d / %d", __func__,
> +		    bridge->streaming, ret);
> +	mutex_unlock(&bridge->lock);
> +
> +	return ret;
> +}
> +
> +static const struct v4l2_subdev_video_ops mipid02_video_ops = {
> +	.s_stream = mipid02_s_stream,
> +};
> +
> +static const struct v4l2_subdev_ops mipid02_subdev_ops = {
> +	.video = &mipid02_video_ops,
> +};
> +
> +static int mipid02_async_bound(struct v4l2_async_notifier *notifier,
> +			       struct v4l2_subdev *s_subdev,
> +			       struct v4l2_async_subdev *asd)
> +{
> +	struct mipid02_dev *bridge = to_mipid02_dev(notifier->sd);
> +	struct i2c_client *client = bridge->i2c_client;
> +	int source_pad;
> +
> +	dev_dbg(&client->dev, "sensor_async_bound call %p", s_subdev);
> +
> +	source_pad = media_entity_get_fwnode_pad(&s_subdev->entity,
> +						 s_subdev->fwnode,
> +						 MEDIA_PAD_FL_SOURCE);
> +	if (source_pad < 0) {
> +		dev_err(&client->dev, "Couldn't find output pad for subdev %s\n",
> +			s_subdev->name);
> +		return source_pad;
> +	}
> +
> +	dev_dbg(&client->dev, "Bnd %s pad: %d\n", s_subdev->name, source_pad);

How about simply "Bound"...? In case you need this.

> +
> +	return media_create_pad_link(&s_subdev->entity, source_pad,
> +				     &bridge->sd.entity, 0,
> +				     MEDIA_LNK_FL_ENABLED |
> +				     MEDIA_LNK_FL_IMMUTABLE);
> +}
> +
> +static const struct v4l2_async_notifier_operations mipid02_notifier_ops = {
> +	.bound		= mipid02_async_bound,
> +};
> +
> +static int mipid02_parse_rx_ep(struct mipid02_dev *bridge)
> +{
> +	struct v4l2_fwnode_endpoint ep;
> +	struct i2c_client *client = bridge->i2c_client;
> +	struct device_node *ep_node;
> +	int ret;
> +
> +	memset(&ep, 0, sizeof(ep));
> +	ep.bus_type = V4L2_MBUS_CSI2_DPHY;
> +	/* parse rx (endpoint 0) */
> +	ep_node = of_graph_get_endpoint_by_regs(bridge->i2c_client->dev.of_node,
> +						0, 0);
> +	if (!ep_node) {
> +		dev_err(&client->dev, "unable to find port0 ep");
> +		ret = -EINVAL;
> +		goto error;
> +	}
> +
> +	ret = v4l2_fwnode_endpoint_alloc_parse(of_fwnode_handle(ep_node), &ep);
> +	if (ret) {
> +		dev_err(&client->dev, "Could not parse v4l2 endpoint %d\n",
> +			ret);
> +		goto error_of_node_put;
> +	}
> +
> +	/* do some sanity checks */
> +	if (ep.bus.mipi_csi2.num_data_lanes > 2) {
> +		dev_err(&client->dev, "max supported data lanes is 2 / got %d",
> +			ep.bus.mipi_csi2.num_data_lanes);
> +		ret = -EINVAL;
> +		goto error_v4l2_fwnode_endpoint_free;
> +	}
> +
> +	/* register it for later use */
> +	bridge->rx = ep;
> +	bridge->rx.link_frequencies = ep.nr_of_link_frequencies == 1 ?
> +		&bridge->link_frequency : NULL;
> +	v4l2_fwnode_endpoint_free(&ep);
> +
> +	/* register async notifier so we get noticed when sensor is connected */
> +	bridge->asd.match.fwnode =
> +		fwnode_graph_get_remote_port_parent(of_fwnode_handle(ep_node));
> +	bridge->asd.match_type = V4L2_ASYNC_MATCH_FWNODE;
> +	of_node_put(ep_node);
> +
> +	v4l2_async_notifier_init(&bridge->notifier);
> +	ret = v4l2_async_notifier_add_subdev(&bridge->notifier, &bridge->asd);
> +	if (ret) {
> +		dev_err(&client->dev, "fail to register asd to notifier %d",
> +			ret);
> +		goto error_fwnode_handle_put;
> +	}
> +	bridge->notifier.ops = &mipid02_notifier_ops;
> +
> +	ret = v4l2_async_subdev_notifier_register(&bridge->sd,
> +						  &bridge->notifier);
> +	if (ret)
> +		v4l2_async_notifier_cleanup(&bridge->notifier);
> +
> +	return ret;
> +
> +error_v4l2_fwnode_endpoint_free:
> +	v4l2_fwnode_endpoint_free(&ep);
> +error_of_node_put:
> +	of_node_put(ep_node);
> +error:
> +
> +	return ret;
> +
> +error_fwnode_handle_put:
> +	fwnode_handle_put(bridge->asd.match.fwnode);
> +
> +	return ret;
> +}
> +
> +static int mipid02_parse_tx_ep(struct mipid02_dev *bridge)
> +{
> +	struct i2c_client *client = bridge->i2c_client;
> +	struct v4l2_fwnode_endpoint ep;
> +	struct device_node *ep_node;
> +	int ret;
> +
> +	memset(&ep, 0, sizeof(ep));
> +	ep.bus_type = V4L2_MBUS_PARALLEL;

You can set the field in variable declaration, and omit memset. The same in
the function above.

> +	/* parse tx (endpoint 2) */
> +	ep_node = of_graph_get_endpoint_by_regs(bridge->i2c_client->dev.of_node,
> +						2, 0);
> +	if (!ep_node) {
> +		dev_err(&client->dev, "unable to find port1 ep");
> +		ret = -EINVAL;
> +		goto error;
> +	}
> +
> +	ret = v4l2_fwnode_endpoint_parse(of_fwnode_handle(ep_node), &ep);
> +	if (ret) {
> +		dev_err(&client->dev, "Could not parse v4l2 endpoint\n");
> +		goto error_of_node_put;
> +	}
> +
> +	of_node_put(ep_node);
> +	bridge->tx = ep;
> +
> +	return 0;
> +
> +error_of_node_put:
> +	of_node_put(ep_node);
> +error:
> +
> +	return -EINVAL;
> +}
> +
> +static int mipid02_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
> +	struct device *dev = &client->dev;
> +	struct mipid02_dev *bridge;
> +	u32 clk_freq;
> +	int ret;
> +
> +	bridge = devm_kzalloc(dev, sizeof(*bridge), GFP_KERNEL);
> +	if (!bridge)
> +		return -ENOMEM;
> +
> +	bridge->i2c_client = client;
> +	v4l2_i2c_subdev_init(&bridge->sd, client, &mipid02_subdev_ops);
> +
> +	/* got and check clock */
> +	bridge->xclk = devm_clk_get(dev, "xclk");
> +	if (IS_ERR(bridge->xclk)) {
> +		dev_err(dev, "failed to get xclk\n");
> +		return PTR_ERR(bridge->xclk);
> +	}
> +
> +	clk_freq = clk_get_rate(bridge->xclk);
> +	if (clk_freq < 6000000 || clk_freq > 27000000) {
> +		dev_err(dev, "xclk freq must be in 6-27 Mhz range. got %d Hz\n",
> +			clk_freq);
> +		return -EINVAL;
> +	}
> +
> +	bridge->reset_gpio = devm_gpiod_get_optional(dev, "reset",
> +						     GPIOD_OUT_HIGH);
> +
> +	ret = mipid02_get_regulators(bridge);
> +	if (ret) {
> +		dev_err(dev, "failed to get regulators %d", ret);
> +		return ret;
> +	}
> +
> +	mutex_init(&bridge->lock);
> +	bridge->sd.flags = V4L2_SUBDEV_FL_HAS_DEVNODE;
> +	bridge->sd.entity.function = MEDIA_ENT_F_VID_IF_BRIDGE;
> +	bridge->pad[0].flags = MEDIA_PAD_FL_SINK;
> +	bridge->pad[1].flags = MEDIA_PAD_FL_SOURCE;
> +	ret = media_entity_pads_init(&bridge->sd.entity, MIPID02_PAD_NB,
> +				     bridge->pad);
> +	if (ret) {
> +		dev_err(&client->dev, "pads init failed %d", ret);
> +		return ret;
> +	}
> +
> +	/* enable clock, power and reset device if available */
> +	ret = mipid02_set_power_on(bridge);
> +	if (ret)
> +		goto entity_cleanup;
> +
> +	ret = mipid02_detect(bridge);
> +	if (ret) {
> +		dev_err(&client->dev, "failed to detect mipid02 %d", ret);
> +		goto power_off;
> +	}
> +
> +	ret = mipid02_parse_tx_ep(bridge);
> +	if (ret) {
> +		dev_err(&client->dev, "failed to parse tx %d", ret);
> +		goto power_off;
> +	}
> +
> +	ret = mipid02_parse_rx_ep(bridge);
> +	if (ret) {
> +		dev_err(&client->dev, "failed to parse rx %d", ret);
> +		goto power_off;
> +	}
> +
> +	ret = v4l2_async_register_subdev(&bridge->sd);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "v4l2_async_register_subdev failed %d",
> +			    ret);
> +		goto unregister_notifier;
> +	}
> +
> +	dev_info(&client->dev, "mipid02 device probe successfully");
> +
> +	return 0;
> +
> +unregister_notifier:
> +	v4l2_async_notifier_unregister(&bridge->notifier);
> +	v4l2_async_notifier_cleanup(&bridge->notifier);
> +power_off:
> +	mipid02_set_power_off(bridge);
> +entity_cleanup:
> +	media_entity_cleanup(&bridge->sd.entity);
> +
> +	return ret;
> +}
> +
> +static int mipid02_remove(struct i2c_client *client)
> +{
> +	struct v4l2_subdev *sd = i2c_get_clientdata(client);
> +	struct mipid02_dev *bridge = to_mipid02_dev(sd);
> +
> +	v4l2_async_notifier_unregister(&bridge->notifier);
> +	v4l2_async_notifier_cleanup(&bridge->notifier);
> +	v4l2_async_unregister_subdev(&bridge->sd);
> +	mipid02_set_power_off(bridge);
> +	media_entity_cleanup(&bridge->sd.entity);
> +
> +	return 0;
> +}
> +
> +static const struct i2c_device_id mipid02_id[] = {
> +	{"st-mipid02", 0},

Could you add whitespaces inside braces?

> +	{},
> +};
> +MODULE_DEVICE_TABLE(i2c, mipid02_id);
> +
> +static const struct of_device_id mipid02_dt_ids[] = {
> +	{ .compatible = "st,st-mipid02" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, mipid02_dt_ids);
> +
> +static struct i2c_driver mipid02_i2c_driver = {
> +	.driver = {
> +		.name  = "st-mipid02",
> +		.of_match_table = mipid02_dt_ids,
> +	},
> +	.id_table = mipid02_id,
> +	.probe    = mipid02_probe,
> +	.remove   = mipid02_remove,
> +};
> +
> +module_i2c_driver(mipid02_i2c_driver);
> +
> +MODULE_AUTHOR("Mickael Guene <mickael.guene@st.com>");
> +MODULE_DESCRIPTION("STMicroelectronics MIPID02 CSI-2 bridge driver");
> +MODULE_LICENSE("GPL v2");

-- 
Kind regards,

Sakari Ailus